Chemical modification and site-directed mutagenesis studies identified that Lys-195 in ADPGlc PPase from E.coli was involved in the binding of substrate glucose 1-P (Glc 1-P) . This residue is highly conserved in every bacterial and plant ADPGlc PPase sequenced to date . In the previous work, it was suggested that the small subunit of the potato tuber ADPGlc PPase might act primarily as a catalytic subunit, while the large subunit as a regulatory subunit. However, it was still quite possible that the Glc 1-P binding site is shared between the large and small subunits. Site-directed mutagenesis was used to discriminate these possibilities. It was found that the Km value for Glc 1-P of the wild type tuber enzyme increased 200-, 550-, 780 -fold by changing the putative lysine residue ( Lys-198 ) to Arg, Ala, Glu, respectively. This indicates that this Lys residue in the smalt subunit performs the same role as the corresponding Lys residue in E.coli. ADPGlc PPase. Site-directed mutagenesis studies on the conserved lys residue on the large subunit of the tuber enzyme will be done in the near future.
|Original language||English (US)|
|State||Published - 1996|
ASJC Scopus subject areas
- Agricultural and Biological Sciences (miscellaneous)
- Biochemistry, Genetics and Molecular Biology(all)
- Cell Biology